The present invention relates to a method of measuring the fluidity of plastic fluids, a method of preparing the same, a method of pouring the same and apparatus for carrying out these methods.
When preparing or constructing residence houses, buildings, civil work structures, furnaces, metallurgical installations, and structural members such as walls, bricks and blocks by using cement, plaster, clay or other refractory substances, plastic fluids are poured or cast or packed into spaces, for example, narrow or crooked passages in which reinforcing iron bars or structural members are arranged or into interstices between aggregates which act as resistive elements to the flow of the plastic fluids. Various authorities, theories, and results of study regarding the fluidity of such plastic fluids have been reported or proposed. Yet accurate analysis has not yet been possible.
More particularly, according to the regulation of the Japanese Institute of Architecture (JASS, ST-701) and the Japanese Institute of Civil Engineering, a flow down testing device termed of P funnel, that is a funnel shaped measuring device having a discharge opening of a predetermined diameter at the bottom is used for determining the fluidity in accordance with the time (flow value) required for the plastic fluid, for example a cement composition, contained in the measuring devices to discharge through the discharge opening.
Of course, such flow value is a measure indicating the fluidity, but according to the result of our test regarding a prepacked mould in which the pouring pressure and other pouring conditions of a hydraulic setting composition such as cement are determined based on the flow value, it was found that it is difficult to establish a definite relationship between the flow value and the pouring conditions. Consequently, even in a composition having a relatively low flow value, it is difficult or impossible to pour it in some cases. In other words, by utilizing the result of measuring the fluidity by the P funnel it is impossible to satisfactorily practice the prepacked process to obtain products of high quality. In case when the pouring is difficult or impossible it is necessary not only to change the method of preparation of the plastic composition such as mortar but also to disassemble the casting mould for exchanging the coarse aggregate. Moreover, the strength and other characteristics of the products are not excellent.
According to the previous theory and research, the viscosity coefficient utilized to determine the fluidity was measured by a rotary viscosimeter. However, as a result of our extensive analysis we have found that the result of measurement of the fluidity of plastic fluids by this method is doubtful.
It has already been reported that cement mortar, paste or the like manifest the characteristics of Bingham fluid, but regarding the flow characteristic of the mortar comprising a complex suspension when it is poured into a mould packed with an aggregate having irregular size and shape no report has yet been made. The Bingham fluid is characterized in that it will flow only when a force larger than a predetermined value is applied to it, and the shear stress acting upon the plastic fluid when it begins to move is termed an initial shear stress yielding value or point. However, no efficient method or device for detecting the initial shear stress yielding value is known. In the past, this value was obtained from the flow speed determined by the P funnel or the viscosity determined by the rotary viscosimeter. In the pouring of a cement mortar into a mould (hereinafter, this term is used to mean not only ordinary moulds but also any spaces or voids of buildings or structures to be filled with cement mortar) the configuration of the voids or interstices in the aggregate such as gravel and crushed stone is extremely complicated so that the flow of the poured cement mortar through the voids is extremely complicated. For this reason, the actual performance of the cement mortar poured into a prepacked mould can never be simply anticipated by the prior art method described above, and it has been necessary to determine the initial shear stress yielding value by many experiments which is of course troublesome and expensive.